Abstract

The nucleation of the superconducting condensate in an Al film deposited on top of a periodic array of microsized Pb rings is investigated using transport measurements. We demonstrate that these Pb rings form tunable pinning sites which can be switched at will to repel or attract vortices in the Al film, depending on their magnetic history. After zero field cooling, a repulsive interaction between the rings and the vortices is observed, while after field cooling, the interaction becomes attractive. The flexibility of such current-induced pinning centers can lead to an enhanced control over the vortex motion.